The research plan proposes 1) to develop a more rapid and highly sensitive inhibition assay for the determination of the relative average affinity of antibody in small concentrations such as exists in external body secretions such as milk. 2) To apply this assay to the analyses of immune milk samples to determine the efficacy of increasing the binding affinity of locally induced secretory IgA antibody by prior oral administration of homologous antigen. The research plan involves the development of a modification of an enzyme-linked immunosorbent assay for the analyses of secretory IgA and of IgG antibody in milk samples collected from lactating rats locally injected with DNP-BGG during pregnancy or without prior oral exposure to the antigen. Methodology involves techniques such as gel-filtration, enzyme-linked immunosorbent assay, antigen synthesis, radial immunodiffusion as well as others. The secretory IgA system of saliva has important potential applications for the prevention or control of dental caries as well as other oral diseases by means of immunization. We propose to develop a new and highly sensitive method which will allow the analysis of IgA affinity for antigen in a secretion. We will apply the assay to the evaluation of the ability to increase the relative average affinity of IgA in a secretion by oral priming. A similar ability to increase the affinity of IgA antibody in saliva may lead to a highly effective means of immunizing against dental caries and other dental diseases.